ABSTRACT
The present study assessed the protein fractions of the milk in 135 mammary quarters with subclinical mastitis caused by Staphylococcus aureus. These quarters were classified in two groups: treated (67) and not treated (68). The antimicrobial drug used for the treatment was gentamicin (150 mg) once a day and for three consecutive days. The herd was situated in the Barretos region, state of São Paulo, Brazil. Mammary quarters were considered cured when samples of milk were negative for the isolation of S. aureus 30 days after the treatment. Fractions of total protein, true protein, casein and whey protein were determined, before and after lactation. Total solids, somatic cell counts and milk production were also analyzed. After the analyses of the data, it was verified that there was no significant difference for total protein, true protein or whey protein after the treatment, while the same difference found in sick mammary quarters for casein, before and after the treatment, was verified for the healthy quarters. In conclusion, the treatment of subclinical mastitis caused by S. aureus during lactation did not produce improvement in the quality of the product when the milk protein levels were analyzed.
KEY WORDS
Milk; antibiotic; protein; mastitis